Quantification of mechanical behavior of rat tail under compression.

BACKGORUND: The development of vibration-induced finger disorders is likely associated with combined static and dynamic responses of the fingers to vibration exposure. To study the mechanism of the disorders, a new rat-tail model has been established to mimic the finger vibration and pressure exposures. However, the mechanical behavior of the tail during compression needs to be better understood to improve the model and its applications. OBJECTIVE: To investigate the static and time-dependent force responses of the rat tail during compression. METHODS: Compression tests were conducted on Sprague-Dawley cadaver rat tails using a micromechanical system at three deformation velocities and three deformation magnitudes. Contact-width and the time-histories of force and deformation were measured. Additionally, force-relaxation tests were conducted and a Prony series was used to model the force-relaxation behavior of the tail. RESULTS: The rat tails' force-deformation and stiffness-deformation relationships were strongly nonlinear and time-dependent. Force/stiffness increased with an increase in deformation and deformation velocity. The time-dependent force-relaxation characteristics of the tails can be well described using a Prony series. CONCULSIONS: We successfully quantified the static and time-dependent force responses of rat tails under compression. The identified mechanical behavior of the tail can help improve the rat-tail model and its applications.

AGREEMENT OF HIP KINEMATICS BETWEEN TWO TRACKING MARKER CONFIGURATIONS USED WITH THE CODA PELVIS DURING ERGONOMIC ROOFING TASKS.

The anterior and posterior iliac spine markers frequently used to define the pelvis, are commonly occluded during three-dimensional (3D) motion capture. The occlusion of these markers leads to the use of various tracking marker configurations on the pelvis, which affect kinematic results. The purpose of this investigation was to examine the agreement of CODA pelvis kinematic results when two different tracking marker configurations were used during roofing tasks. 3D motion data were collected on seven male subjects while mimicking two roofing tasks. Hip joint angles (HJAs) were computed using the CODA pelvis with two different tracking marker configurations, the trochanter tracking method (TTM), and virtual pelvis tracking method (VPTM). Agreement between tracking marker configurations was assessed using cross-correlations, bivariate correlations, mean absolute differences (MADs), and Bland-Altman (BA) plots. The correlations displayed no time lag and strong agreement (all r > 0.83) between the HJA from the VPTM and TTM, suggesting the timing occurrence of variables are comparable between the two tracking marker configurations. The MAD between the VPTM and TTM displayed magnitude differences, but most of the differences were within a clinically acceptable range. Caution should still be used when comparing kinematic results between various tracking marker configurations, as differences exist.

Changes in Youth Baseball Pitching Biomechanics: A 7-Year Longitudinal Study.

BACKGROUND: Pitching biomechanics are associated with performance and risk of injury in baseball. Previous studies have identified biomechanical differences between youth and adult pitchers but have not investigated changes within individual young pitchers as they mature. HYPOTHESIS: Pitching kinematics and kinetics will change significantly during a youth pitcher's career. STUDY DESIGN: Descriptive laboratory study. METHODS: Pitching biomechanics were captured in an indoor laboratory with a 12-camera, 240-Hz motion analysis system for 51 youth pitchers who were in their first season of organized baseball with pitching. Each participant was retested annually for the next 6 years or until he was no longer pitching. Thirty kinematic and kinetic parameters were computed and averaged for 10 fastballs thrown by each player. Data were statistically analyzed for the 35 participants who were tested at least 3 times. Within-participant changes for each kinematic and kinetic parameter were tested by use of a mixed linear model with random effects ( P < .05). Least squares means for sequential ages were compared via Tukey's honestly significant difference test ( P < .05). RESULTS: Three kinematic parameters that occur at the instant of foot contact-stride length, lead foot placement to the closed side, and trunk separation-increased with age. With age, shoulder external rotation at foot contact decreased while maximum shoulder external rotation increased. Shoulder and elbow forces and torques increased significantly with age. Year-to-year changes were most significant between 9 and 13 years of age for kinematics and between 13 and 15 years for normalized kinetics (ie, scaled by bodyweight and height). CONCLUSION: During their first few years, youth pitchers improve their kinematics. Elbow and shoulder kinetics increase with time, particularly after age 13. Thus, prepubescent pitchers may work with their coaches to improve the motions and flexibility of the players' bodies and the paths of their arms. Once proper mechanics are developed, adolescent pitchers can focus more on improving strength and power.

'With a bit of tweaking we could be great'. An exploratory study of the perceptions of students on working with older people in a preregistration BSc (Hons) Nursing course.

BACKGROUND: With ageing demographics, it is important that nurse education curriculum can prepare students to work with older people. AIMS AND OBJECTIVES: To explore students' perceptions of working with older people and the extent to which their preregistration curriculum is preparing them for this role. DESIGN: A qualitative research design, incorporating focus groups in data collection. METHODS: Four focus groups were held in January 2011, involving a total of 32 students undertaking a preregistration BSc (Hons) nursing degree course. RESULTS: An overt focus in the preregistration curriculum on acute and critical care and perceived deficits in care of older people content left some students feeling underprepared to work with older people and to challenge ritualistic practice. Clinical placement experience and mentor support appeared to be influencing students' decisions about whether they would consider working with older people in the future. CONCLUSION: Education providers should ensure that students are adequately prepared to work with older people and that students are supported when they observe poor practice. A finding that observation of ritualistic practice could prompt some students to consider working with older people, warrants further research. Implications for practice. Nurse educators should evaluate the content and delivery of their preregistration courses to ensure that the prerequisite knowledge, skills and attitudes required to work with older people are accorded appropriate value and attention.

The Canadian National Retirement Risk Index: employing statistics Canada's LifePaths to measure the financial security of future Canadian seniors.

This article measures a Canadian National Retirement Risk Index (NRRI). Originally developed by the Center for Retirement Research at Boston College, the NRRI is a forward-looking measure that evaluates the proportion of working-aged individuals who are at risk of not maintaining their standard of living in retirement. The Canadian retirement income system has been very effective in reducing elderly poverty, but our results suggest that it has been much less successful in maintaining the living standards of Canadians after retirement. Since the earlier years of the new millennium, we find that approximately one-third of retiring Canadians have been unable to maintain their working-age consumption after retirement­a trend that is projected to worsen significantly for future Canadian retirees. The release of the Canadian NRRI is timely given the widespread concern that the current Canadian retirement income system is inadequate. Many proposals have recently emerged to extend and/or enhance Canadian public pensions, and the NRRI is a tool to test their merit. The methodology underlying the Canadian NRRI is uniquely sophisticated and comprehensive on account of our employment of Statistics Canada's LifePaths, a state-of-the-art stochastic microsimulation model of the Canadian population. For instance, the Canadian NRRI is novel in that it models all of the relevant sources of consumption before and after retirement, while accounting for important features that are typically neglected in retirement adequacy studies such as family size, the variation of consumption over a person's lifetime, and the heterogeneity among the life courses of individuals.